This proposal is a request for continued partial funding of the Flow Cytometry Core Facility (FACS Core) within the UAB AIDS Center. The primary purposes of the FACS Core are to make accessible to AIDS Center investigators the equipment, trained personnel, and expertise to perform cell analysis and purification with state-of-the-art equipment and techniques on a reasonable cost for services basis, and to offer these services in a facility capable of handling potentially infectious material. The FACS Core serves over 30 individual investigators per year, with over 85% of actual booked time being used by AIDS Center members. At the present time, the core contains a FACStar single laster four parameter, two color cytometer/sorter. In the near future, using funds obtained from the UAB Health Services Foundation, this instrument will be replaced with a FACStar/plus six parameter, dual laser cytometer/sorter. The FACS Core and the Flow Cytometry Core Facility of the Multipurpose Arthritis & Musculoskeletal Diseases Center are operated jointly, an arrangement which results in improved service to investigators through increased flexibility in equipment and personnel. The two core facilities jointly employ two individuals who are both experienced cytometer operators. Funds are requested to ensure stable support for 50% of the operators' salaries, continuing education for the operators, and the cytometer maintenance contract. The requested level of support will be sufficient to cover slightly more than 50% of the actual cost of operating the FACS Core. This will allow the present rate of $50/hour for AIDS Center investigators to be sustained into the foreseeable future.